Thursday, August 2, 2012

Alternatives to VXLAN

NVGRE

NVGRE (Network Virtualization Generic Routing Encapsulation)
achieves the same functional goal as VXLAN on the network, however the encapsulation
of VLAN traffic is done on the virtualised server instead. In essence the network VLAN limitations are
overcome by application software.

The server builds a gre tunnel and the virtual subnet id is
included in the GRE header.Each virtual
machine is mapped to a host PA (physical address).End to end communication is completed over
existing networks that are essentially unaware of the encapsulated payloads and
server vlan mappings.

IP Rewrite

An alternative approach to GRE tunnelling is ‘IP rewrite’.
This solution requires each virtual server has its own IP address. This ip
address is rewritten to a physical ip address for transport across the
network.This mapping is reversed on
reaching the destination.

CISCO OTVOTV or Overlay Transport Virtualisation is Cisco's proprietary solution to extending VLANs over IP networks. It encapsulates L2 within IP allowing VLANs to be tunneled over a routed IP network. It is currently enabled on the NEXUS OS.

TRILL

Transparent Interconnection of Lots Of Links or TRILL, enables
extension of L2 domains, through use of RBridges or (Routing Bridges). TRILL RBridges communicate with a link state
protocol, however this executes within
the L2 domain i.e. no ip addresses are required. RBridges have knowledge of the topology
consisting of all the RBridges and all the links between RBridges.

When an RBridge receives an Ethernet frame from an end node it
encapsulates the frame in a TRILL header, addressing the packet to the RBridge with
the destination MAC attached to it. The
destination RBridge performs the decapsulation before sending the packet
onwards.

TRILL like the other technoloigies described enables a large L2
cloud to be created with a common subnet. Therefore hosts within the L2 cloud
do NOT needto change their ip address
if they relocate. TRILL is an ietf standard.